added check in SessionTrans.begin() that the underlying unit of work is still the current uow

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/sqlalchemy/mapping/objectstore.py b/lib/sqlalchemy/mapping/objectstore.py
index 6b3d7f034..d6b476562 100644
--- a/lib/sqlalchemy/mapping/objectstore.py
+++ b/lib/sqlalchemy/mapping/objectstore.py
@@ -98,6 +98,8 @@ class Session(object):
         uow = property(lambda s:s.__uow, doc="returns the parent UnitOfWork corresponding to this transaction.")
         def begin(self):
             """calls begin() on the underlying Session object, returning a new no-op SessionTrans object."""
+            if self.parent.uow is not self.uow:
+                raise InvalidRequestError("This SessionTrans is no longer valid")
             return self.parent.begin()
         def commit(self):
             """commits the transaction noted by this SessionTrans object."""